A diffusion barrier layer and semiconductor device containing same are described herein. More particularly, a novel diffusion barrier layer formed from silicon, carbon, nitrogen and hydrogen with the nitrogen being more concentrated near the lower and upper surfaces of the diffusion barrier layer, i.e., non-uniformly distributed throughout, and semiconductor devices containing such layers are described herein. Also described is a method for manufacturing the semiconductor device containing the diffusion barrier layer.
Generally, semiconductor devices include a plurality of circuits which form an integrated circuit. Integrated circuits can be useful for computers and electronic equipment and can contain millions of transistors and other circuit elements that can be fabricated on a single silicon crystal semiconductor device, i.e., chip. For the device to be functional, a complex network of signal paths will normally be routed to connect the circuit elements distributed on the surface of the device. Efficient routing of these signals across the device can become more difficult as the complexity and number of the integrated circuits are increased. Thus, the formation of multi-level or multi-layered interconnection schemes such as, for example, dual damascene wiring structures, have become more desirable due to their efficacy in providing high speed signal routing patterns between large numbers of transistors on a complex semiconductor chip.
When fabricating integrated circuit wiring with a multi-layered scheme, an insulating or dielectric material, such as silicon oxide, will normally be patterned with several thousand openings to create conductive line openings and/or via openings using photoprocessing techniques, e.g., photolithography with subsequent etching by a plasma process. These via openings are typically filled with a conductive metal material, e.g., aluminum, copper, etc., to interconnect the active and/or passive elements of the integrated circuits. The semiconductor device is then polished to level its surface.
A diffusion barrier layer formed from, e.g., silicon nitride with the nitrogen being uniformly distributed throughout the layer, is then normally deposited over the planarized surface featuring the dielectric material and conductive metal material. Next, a dielectric material is deposited over the diffusion barrier layer, via and conductive line openings are created within the dielectric and barrier layers as before, another conductive metal material is deposited within the openings and another diffusion barrier layer is deposited thereon. The process is then repeated to fabricate a multi-layer interconnect wiring system. The diffusion barrier layers act as an adhesive for keeping the successive layers of the interconnect structure together. However, several problems exist when employing a diffusion barrier layer formed from silicon and nitrogen, i.e., silicon nitride, where the nitrogen is uniformly distributed throughout. Firstly, the diffusion barrier layer does not provide optimum adhesion thereby causing the risk of delamination in the semiconductor device during fabrication or service. Secondly, this type of diffusion barrier layer also causes the semiconductor device to possess a relatively high dielectric constant, typically between 6 and 7, thereby resulting in a higher capacitance between the conductive metal material causing the electric signals to travel at a slower speed with increased cross-talk through the interconnection wiring patterns.
It would be desirable to provide a semiconductor device containing a diffusion barrier layer that can provide a robust adhesion between the interconnection layers while also maintaining a relatively low dielectric constant for the device thereby allowing the electric signals to travel faster therethrough.
A novel diffusion barrier layer has been discovered. The novel diffusion barrier layer for use in semiconductor devices has an upper surface, a lower surface and a central portion and includes silicon, carbon, nitrogen and hydrogen with the nitrogen being non-uniformly distributed throughout the diffusion barrier layer, i.e., more concentrated near the lower and upper surfaces of the barrier layer as compared to the central portion of the diffusion barrier layer. Thus, the novel layer may be described as a trilayer with the middle layer comprised primarily of silicon, carbon and hydrogen and the upper and lower layers being comprised of nitrogen, silicon, carbon, hydrogen and, optionally, oxygen.
A semiconductor device containing the diffusion barrier layer includes a substrate containing a first set of conductive metal elements, a first diffusion barrier layer applied to at least a portion of the substrate in contact with the conductive metal elements, the diffusion barrier layer having an upper surface, a lower surface and a central portion and being formed from silicon, carbon, nitrogen and hydrogen with the nitrogen being non-uniformly distributed throughout. Thus, for example, the nitrogen is concentrated near the lower and upper surfaces of the diffusion barrier layer as compared to the central portion of the diffusion barrier layer. The semiconductor device may also include a dielectric layer applied on the first diffusion barrier layer, line and via openings formed through both the dielectric layer and first diffusion barrier layer to expose the surface of at least one of the conductive metal elements so that a conductive metal material deposited within and filling the line and via openings provides a second set of electrical contact conductive metal elements. Optionally, a second diffusion barrier layer is applied in contact with at least a portion of the top surface of the second set of conductive metal elements, the diffusion barrier layer having an upper surface, a lower surface and a central portion and being formed from silicon, carbon, nitrogen and hydrogen with the nitrogen being non-uniformly distributed throughout.
A method for making the semiconductor device has also been discovered which includes the steps of:
a) forming a first diffusion barrier layer on a semiconductor substrate containing a first set of conductive metal elements, the diffusion barrier layer having an upper surface, a lower surface and a central portion and comprising silicon, carbon, nitrogen and hydrogen and being deposited such that the nitrogen is non-uniformly distributed throughout;
b) forming a dielectric layer on at least a portion of the first diffusion barrier layer;
c) forming line and via openings in the dielectric layer and diffusion barrier layer to expose the top surface of at least one of the conductive metal elements in the first set thereof;
d) depositing a conductive metal material within and filling the line and via openings to form a second set of conductive metal elements; and,
e) forming a second diffusion barrier layer over the top surfaces of the second set of conductive metal elements, the diffusion barrier layer having an upper surface, a lower surface and a central portion and comprising silicon, carbon, nitrogen and hydrogen with the nitrogen being non-uniformly distributed throughout.
The semiconductor device described herein containing a diffusion barrier layer formed from silicon, carbon, nitrogen and hydrogen with the nitrogen being non-uniformly distributed throughout the diffusion barrier layer advantageously possesses a low dielectric constant thereby causing the electric signals generated by the device to travel at a faster rate with reduced cross-talk while the diffusion barrier layer acts as an adhesive such that the semiconductor device is held together more robustly for an extended period of time.